In the manufacture of yarn, the usual process comprises feeding raw cotton fiber into a carding machine through a feed system such as a feed roll and a licker-in to the main large cylinder for the purpose of refining and parallelizing the fibers. The parallel fibers are removed from the main cylinder in the form of a continuous web by a smaller doffing cylinder, and the web is taken from the doffer to a funnel or trumpet which gathers the web into a sliver. The sliver moves from the trumpet between calendar rolls and is directed through a coiler head and into a coiler can where the sliver is coiled for further storage, handling and ultimate removal for further processing into yarn.
In order to prevent the web and sliver from breaking or tearing during the start-up procedures of a carding machine, the carding machine is run at a relatively slow speed. Although the slow speeds allow continuous production of the sliver, the production rate is slow. Some carding machines have included means for varying the doffer speed, and after the sliver is made up to the coiler can the drive system is manually shifted to increase the production rate. The two speed prior art systems have not been very satisfactory since only two fixed speeds of operation are provided and it is required to replace the gears of a machine to change the high production rate of the machine. Moreover, the typical high speed to low speed production rate in most operational carding machines is three to one and produces 23 pounds of cotton per hour at slow speed production and 69 pounds per hour at high speed production, and when a gear replacement is made to increase the high speed production, the low speed operation is also proportionately increased, making it more difficult for the card operator to make up the sliver to the coiler can. Also, the use of cumbersome driving belts and other elements associated with these systems occupy a substantial amount of floor space adjacent the machine and most driving systems cause the doffer to continue rotating after the system has been deactivated, which results in the production of waste. The shift from low to high speed production in the prior art carding machines is abrupt and causes imperfections in the resulting sliver.